const _global =
  typeof window === 'object' && window.window === window
    ? window
    : typeof self === 'object' && self.self === self
    ? self
    : typeof global === 'object' && global.global === global
    ? global
    : this

function bom(blob, opts) {
  if (typeof opts === 'undefined') opts = { autoBom: false }
  else if (typeof opts !== 'object') {
    console.warn('Deprecated: Expected third argument to be a object')
    opts = { autoBom: !opts }
  }

  // prepend BOM for UTF-8 XML and text/* types (including HTML)
  // note: your browser will automatically convert UTF-16 U+FEFF to EF BB BF
  if (opts.autoBom && /^\s*(?:text\/\S*|application\/xml|\S*\/\S*\+xml)\s*;.*charset\s*=\s*utf-8/i.test(blob.type)) {
    return new Blob([String.fromCharCode(0xfeff), blob], { type: blob.type })
  }
  return blob
}

function download(url, name, opts) {
  var xhr = new XMLHttpRequest()
  xhr.open('GET', url)
  xhr.responseType = 'blob'
  xhr.onload = function () {
    saveAs(xhr.response, name, opts)
  }
  xhr.onerror = function () {
    console.error('could not download file')
  }
  xhr.send()
}

function corsEnabled(url) {
  var xhr = new XMLHttpRequest()
  // use sync to avoid popup blocker
  xhr.open('HEAD', url, false)
  try {
    xhr.send()
  } catch (e) {}
  return xhr.status >= 200 && xhr.status <= 299
}

// `a.click()` doesn't work for all browsers (#465)
function click(node) {
  try {
    node.dispatchEvent(new MouseEvent('click'))
  } catch (e) {
    var evt = document.createEvent('MouseEvents')
    evt.initMouseEvent('click', true, true, window, 0, 0, 0, 80, 20, false, false, false, false, 0, null)
    node.dispatchEvent(evt)
  }
}

// Detect WebView inside a native macOS app by ruling out all browsers
// We just need to check for 'Safari' because all other browsers (besides Firefox) include that too
// https://www.whatismybrowser.com/guides/the-latest-user-agent/macos
const isMacOSWebView =
  /Macintosh/.test(navigator.userAgent) &&
  /AppleWebKit/.test(navigator.userAgent) &&
  !/Safari/.test(navigator.userAgent)

function save() {
  if ('download' in HTMLAnchorElement.prototype && !isMacOSWebView) {
    return function (blob, name, opts) {
      var URL = _global.URL || _global.webkitURL
      var a = document.createElementNS('http://www.w3.org/1999/xhtml', 'a')
      name = name || blob.name || 'download'
      a.download = name
      a.rel = 'noopener' // tabnabbing
      // TODO: detect chrome extensions & packaged apps
      // a.target = '_blank'
      if (typeof blob === 'string') {
        // Support regular links
        a.href = blob
        if (a.origin !== location.origin) {
          corsEnabled(a.href) ? download(blob, name, opts) : click(a, (a.target = '_blank'))
        } else {
          click(a)
        }
      } else {
        // Support blobs
        a.href = URL.createObjectURL(blob)
        setTimeout(function () {
          URL.revokeObjectURL(a.href)
        }, 4e4) // 40s
        setTimeout(function () {
          click(a)
        }, 0)
      }
    }
  } else if ('msSaveOrOpenBlob' in navigator) {
    return function (blob, name, opts) {
      name = name || blob.name || 'download'
      if (typeof blob === 'string') {
        if (corsEnabled(blob)) {
          download(blob, name, opts)
        } else {
          var a = document.createElement('a')
          a.href = blob
          a.target = '_blank'
          setTimeout(function () {
            click(a)
          })
        }
      } else {
        navigator.msSaveOrOpenBlob(bom(blob, opts), name)
      }
    }
  } else {
    return function (blob, name, opts, popup) {
      popup = popup || open('', '_blank')
      if (popup) {
        popup.document.title = popup.document.body.innerText = 'downloading...'
      }
      if (typeof blob === 'string') return download(blob, name, opts)
      var force = blob.type === 'application/octet-stream'
      var isSafari = /constructor/i.test(_global.HTMLElement) || _global.safari
      var isChromeIOS = /CriOS\/[\d]+/.test(navigator.userAgent)
      if ((isChromeIOS || (force && isSafari) || isMacOSWebView) && typeof FileReader !== 'undefined') {
        // Safari doesn't allow downloading of blob URLs
        var reader = new FileReader()
        reader.onloadend = function () {
          var url = reader.result
          url = isChromeIOS ? url : url.replace(/^data:[^;]*;/, 'data:attachment/file;')
          if (popup) popup.location.href = url
          else location = url
          popup = null // reverse-tabnabbing #460
        }
        reader.readAsDataURL(blob)
      } else {
        var URL = _global.URL || _global.webkitURL
        var url = URL.createObjectURL(blob)
        if (popup) popup.location = url
        else location.href = url
        popup = null // reverse-tabnabbing #460
        setTimeout(function () {
          URL.revokeObjectURL(url)
        }, 4e4) // 40s
      }
    }
  }
}


export const saveAs = save()

// if (typeof module !== 'undefined') {
//   module.exports = saveAs
// }
